Phosphorylation of the movement protein TGBp1 of Potato virus X by a CK2-like protein kinase.

MÓDENA N., ZELADA A. AND MENTABERRY A.

Iguazú, Misones, Argentina

Congreso; XL Reunión Anual de Sociedad Argentina de Investigación Bioquímica (S.A.I.B); 2004

Sociedad Argentina de Investigación Bioquímica

Potato virus X (PVX) is a member of the potexvirus whose RNA genome codes for the viral replicase, three movement proteins (MPs: TGBp1, TGBp2 and TGBp3) and the viral capsid protein (CP). The principal role of MPs is to assist in the spreading of viral progeny from cell to cell and over long distances. Growing evidences suggests that phosphorylation events can regulate MP functions. We have demonstrated that PVX TGBp1 is phosphorylated on serine and threonine residues by a kinase present in both PVX-infected and non-infected Nicotiana tabacum. In the present work we show that this kinase activity presents characteristics of casein kinase CK2: it is inhibited by heparin and activated by polylysine and is able to use both ATP and GTP as a phosphoryl donors. We also demonstrate that TGBp1 is phosphorylated by a human CK2 a subunit and a partially purified N. tabacum CK2. In addittion, in situ phosphorylation assays show that native PVX TGBp1 is phosphorylated in plant extracts of PVX-infected plants by a CK2-like cellular kinase. Based on comparative analyses of potexvirus TGBp1 we have developed two different PVX mutant on threonine residues. Preliminary infection experiments show that the mutants are not able to produce systemic infection. These results shows that TGBp1 is phosphorylated  by a host kinase closely related to CK2.